Direct Air Capture: Can Vacuuming CO2 Save the Climate?

For decades, the concept of giant machines sucking carbon dioxide out of the sky sounded like science fiction. Today, it is a rapidly growing industry backed by billions of dollars in government funding and private investment. Direct Air Capture (DAC) technology has moved from theoretical whiteboards to operational facilities in the real world. This article breaks down the economics, the energy physics, and the specific companies leading the charge to see if “vacuuming” the atmosphere is a viable solution for climate change.

The Rise of the "Mammoth": A Case Study in Scale

To understand the current state of DAC, you have to look at Iceland. In May 2024, a Swiss company named Climeworks switched on “Mammoth,” currently the world’s largest operating direct air capture and storage plant.

Located on the dormant Hellisheiði volcano, Mammoth is designed to capture up to 36,000 tons of CO2 per year once fully operational. This dwarfs its predecessor, “Orca,” which opened in 2021 with a capacity of 4,000 tons annually.

The process used by Climeworks is specific and tangible:

  1. Capture: Giant fans pull air through collectors containing a specialized filter material (solid sorbent). CO2 sticks to the filter like a magnet.
  2. Release: Once the filter is full, the collector closes and is heated to roughly 100°C (212°F) using geothermal energy. This releases the concentrated CO2.
  3. Storage: Climeworks partners with an Icelandic company called Carbfix. They dissolve the CO2 in water and pump it deep underground into basalt rock formations. Within two years, the gas reacts with the rock and turns into stone, permanently removing it from the atmosphere.

While 36,000 tons sounds impressive, it is a drop in the bucket compared to global emissions, which measure in the billions of tons. However, the technology proves that the mechanics work.

The Price of Pure Air: Economics and the $100 Goal

The biggest hurdle for DAC is not physics. It is finance. Currently, the cost to remove one ton of CO2 varies wildly but generally sits between \(600 and \)1,000.

For this technology to be commercially viable on a global scale, the industry standard target is $100 per ton. This is the “Carbon Negative Shot” goal set by the U.S. Department of Energy.

Why is it so expensive?

Capturing carbon from a smokestack is easier because the concentration of CO2 is high (around 10% to 15%). Capturing it from the open air is much harder because CO2 makes up only 0.04% of the atmosphere. The machines have to process massive volumes of air to catch a small amount of carbon.

Who is paying for it?

Right now, the market is driven by voluntary buyers willing to pay a premium for high-quality removal credits.

  • Microsoft: The tech giant is a major customer for Climeworks and has also signed a deal with Heirloom Carbon.
  • Stripe, Shopify, and H&M: These companies contribute to the “Frontier” fund, an advance market commitment to buy over $1 billion of permanent carbon removal.

Comparing Technologies: Liquid vs. Solid

Not all vacuuming methods are the same. There are two primary approaches dominating the sector right now.

1. Solid Sorbent (Climeworks, Heirloom)

  • Method: Uses solid filters that chemically bind with CO2 at ambient temperatures.
  • Energy: Requires lower grade heat (around 80°C to 100°C) to release the gas.
  • Pros: Can utilize waste heat or geothermal energy.
  • Cons: The filters degrade over time and need replacement.

2. Liquid Solvent (Carbon Engineering / 1PointFive)

  • Method: Air passes over a liquid chemical solution (usually potassium hydroxide) that traps the carbon.
  • Energy: This process requires a second step involving a calciner that reaches temperatures of up to 900°C (1,650°F).
  • Scale: This technology is being deployed at the “Stratos” plant in Texas. Owned by 1PointFive (a subsidiary of Occidental Petroleum), Stratos is currently under construction and aims to capture 500,000 tons per year.
  • Pros: Better suited for massive industrial scale.
  • Cons: High temperature requirements often necessitate the use of natural gas, which creates its own emissions that must also be captured.

The Role of Government Policy

The private sector cannot lower the price alone. Government intervention has recently changed the math for investors.

In the United States, the Inflation Reduction Act (IRA) significantly boosted the “45Q” tax credit. The government now offers up to \(180 per ton for CO2 captured from the air and permanently stored. This creates a guaranteed revenue stream for developers. If a company can get their costs down to \)250 per ton, the $180 credit covers the majority of the expense, making the remaining gap easier to close with private buyers.

Additionally, the U.S. Department of Energy announced $3.5 billion in funding for Regional Direct Air Capture Hubs. The first two major awards went to the Cypress project in Louisiana (using Battelle and Heirloom technology) and the South Texas DAC Hub (using Occidental’s technology).

Evaluating Energy Efficiency

The energy criticism is valid. Thermodynamics dictates that separating mixed gases requires energy. Studies suggest that removing a gigaton (1 billion tons) of CO2 could require a significant percentage of current global renewable energy production.

  • Geothermal Advantage: In Iceland, Climeworks uses geothermal energy, which is clean and abundant locally.
  • The Texas Dilemma: Plants in Texas may rely on natural gas or grid electricity. If the grid is powered by coal or gas, the net benefit of the capture drops.

For DAC to “save the climate,” the plants must be powered by zero-carbon sources (nuclear, wind, solar, or geothermal) that are not being diverted from other essential uses.

Frequently Asked Questions

Is Direct Air Capture safe?

Yes, the capture process itself is industrial but generally safe. The storage aspect—pumping CO2 underground—is a well-understood process used in the oil and gas industry for decades. When injected into basalt (like in Iceland), the mineralization process renders leaks impossible once the gas turns to stone.

Can trees do the same job for free?

Trees are essential, but they are part of the fast carbon cycle. When trees rot or burn, they release the CO2 back into the air. DAC combined with deep geological storage puts carbon back into the slow carbon cycle, locking it away for millions of years. Furthermore, trees require vast amounts of land. DAC plants have a much smaller physical footprint per ton of carbon removed.

Will this encourage oil companies to keep polluting?

This is a common concern known as “moral hazard.” Critics worry that oil companies invest in DAC to justify continuing fossil fuel extraction. However, the Intergovernmental Panel on Climate Change (IPCC) has stated that carbon removal is now unavoidable if we want to limit warming to 1.5°C or 2°C, simply because we have already emitted too much. It is not a replacement for cutting emissions; it is a necessary addition.